1. The minimum grain size resulting from induction heating is determined by the initial size of the austenite grains, which, in turn, depends on the size of the elements of the original structure 2. Changes in the rate of induction heating between 8 and 1000 deg/sec do not affect the size of the initial grains. Further growth of the grains with increasing temperatures depends on the heating rate: low rates and high temperatures may result in considerable grain growth. 3. The use of small-grained steel makes it possible to widen the range of temperatures and the induction heating rates resulting in small austenite grains. The decrease of the size of austenite grains from grade 8 to grade 12 decreases the hardenability and increases the strength of steels with a martensitic structure. Small austenite grains can be obtained in quenched steel regardless of the heating rate. 4. The use of small-grained steel and the application of the optimum conditions of induction heating result in a considerable increase in the strength of machine parts.